Schottky diodes have been used for many years in the semiconductor industry in, for example, electronic systems, such as amplifiers, receivers, control and guidance systems, power and signal monitors, and as rectifiers and clamps in RF circuits. Commercial applications include radiation detectors, imaging devices, and wired and wireless communications products. A Schottky diode can be formed by the connection of a metal or silicide layer to a doped semiconductor layer. A Schottky junction (or Schottky barrier) is formed at the junction of the metal layer and the doped semiconductor layer.
Schottky diodes are prone to high electric field regions at the ion implant regions where the metal or silicide of the diode structure meets the isolation structure. Typically, these electric field regions prohibit the diode from performing at its optimum characteristic level. Parameters that are adversely affected by this field include the reverse bias leakage current and breakdown voltage.
Current approaches at eliminating the high electric field regions near the isolation barrier consist of adding a pn diode guard ring at the edge of the isolation structure. In the case of an n-type Schottky diode, the p-type guard rings are implanted into the n-type regions at the perimeter of the Schottky contact region. This provides for a better diode; however, it increases the capacitance of the device and adds a minority carrier injection mechanism into the device, which in turn increases the diode recovery time. Additionally, fabrication of such a guard ring typically requires an additional masking step.